This invention relates to on/off sprinklers for use in sprinkler fire-fighting equipment.
It is an object of the present invention to provide an on/off sprinkler which is simpler in construction and less likely to become, due to the passage of time, non-operational than known on/off sprinklers, due, for example, to the omission of relatively sliding components in the sprinkler construction.
According to the present invention there is provided an on/off sprinkler comprising a body having a fire extinguishant inlet spaced from a fire extinguishant outlet, a flexible diaphragm within the body normally isolating the inlet from the outlet save for a leakage path between the inlet and an intermediate chamber defined by the diaphragm and body, whereby an extinguishant pressure balance is attained at both sides of the diaphragm, and normally-closed exhaust port means openable, upon attainment of a predetermined first temperature value, to cause extinguishant pressure imbalance with consequent diaphragm movement connecting the inlet to the outlet, and closable upon attainment of a predetermined second temperature value.
Preferably, the leakage path is provided by a leakage orifice in the diaphragm.
Preferably also, the diaphragm is spring-urged to its isolating position to assist pressure balance.
Preferably also, the diaphragm in its isolating position abuts an internal seat in the hollow body.
The exhaust port means may comprise a port from the intermediate chamber normally closed by an open/close valve movable under the influence of a heat sensitive device external of the sprinkler body.
The heat sensitive device may be a bimetallic disc connected to the valve by a stem.
An extinguishant deflector is preferably provided on the valve stem between the valve and bimetallic disc to prevent cooling of the latter on intermediate chamber exhaustion.
The intermediate chamber may have first and second exhaust ports normally closed by first and second valves releasably held in closed position by first and second heat sensitive devices, one of said valves being an open/close valve while the other is a close-to-open valve, a third and open-to-close valve being held in the intermediate chamber and being adapted to replace and close the exhaust port normally closed by the close-to-open valve on exhaustion of the intermediate chamber.
The open-to-close valve is preferably held clear of its exhaust port by the open/close valve so that, when there is predetermined temperature decrease, the open-to-close valve will have closed its exhaust port and the open/close valve will have returned to its original position to close its exhaust port.
The intermediate chamber may have an exhaust port normally closed by a close-to-open valve openable due to the action of a heat sensitive device, a second and open-to-close valve movable to close the exhaust port being held clear of the latter by a second heat sensitive device until the predetermined temperature decrease is achieved.
The second heat sensitive device preferably operates a pivotal lever adapted to maintain the open-to-close valve clear of the exhaust port.
Alternatively, the second heat sensitive device operates a bellows arrangement operable to maintain the open-to-close valve clear of the exhaust port.